A wind turbine generator is an apparatus in which a rotor head including a wind turbine blade is rotated by wind power, and a generator driven by increasing the speed of the rotation with a gear box or the like generates electricity.
The above-described rotor head is mounted to an end of a nacelle that is provided on a wind turbine tower (hereinafter referred to as “tower”) and can yaw, and supported rotatably around a substantially horizontal, lateral rotation axis.
A conventional wind turbine generator includes a pitch control device that changes a pitch angle of a wind turbine blade depending on wind speed. The pitch control device is a device for setting an optimum pitch angle of each wind turbine blade depending on wind speed and controlling rotational speed of a rotor head.
For the pitch control device to be able to adjust a pitch angle of the wind turbine blade, a blade rotating ring bearing is used that rotatably supports the wind turbine blade on the rotor head. The blade rotating ring bearing uses a rolling bearing with a rolling element (such as a ball bearing or a roller) provided between an inner ring and an outer ring.
To the blade rotating ring bearing, lubricant oil (grease) for lubricating a bearing slide portion is supplied. An automatic grease supply device installed in the rotor head is used to supply the lubricant oil, and degraded lubricant oil is pushed out by supplied grease and recovered as discharged grease in a reservoir tank in the rotor head.
Patent Literature 1 listed below describes automatic grease supply of a wind turbine in which a control device controls a grease supply pump to discharge grease from a nozzle and thus automatically supply the grease without contact.